Esters of aliphatic dibasic acids and ether-alcohols containing a branched chain in the glycol group



Patented Oct. 2, 1 951 OFFICE ESTERS OF ,AL IPHATIC DIBASIC ACIDS AND ETHER-ALCOHOLS CONTAINING A BRANCHED CHAIN IN THE GLYCOL GROUP Paul V. Smith, J 11., Westfield, and Fred Knoth, Jr., Union, N. J. assignors to Standard Oil Development'Company, a corporation of Delaware No Dra wing. Application August 3, 1948,

Serial No. 42,334

-5 Claims. 1 1

This invention relates to a new class of organic compounds consisting of esters of a type to be specified hereinafter, the same being found to possess properties which indicate that these compounds are particularly suitable for use as synthetic lubricants.

In the lubricant art, considerable progress has been realized in recent years in the production of lubricants characterized by one or more speciflc properties and adapted for particular uses. In the main, this progress can be attributed to two developments: the first, new refining procedures, and the second, addition agents capable of imparting particular properties to available lubricants. Thus, viscosity index improvers and pour depressants are added to automotive lubricants to render the lubricants more adaptable to wide changes in temperature conditions, while other agents are added to improve the load carrying properties of a lubricant which is to be employed, for example, under extreme pressure conditions. u

Recently, in an effort to obtain superior lubricants endowed with specific and superior characteristics, a new field has been explored, namely, the synthesis of lubricants from various materials. Esters represent one class of materials which have attracted unusual interest as synthetic lubricants. In general, they are characterized by higher viscosity indices and lower pour points than mineral oils of corresponding viscosity. The esters described in the present specification have been found to exhibit very low pour points and high viscosity indices. *Lubricants possessing such properties are of special value to the lubrication of engines which are subjected to high temperatures such as combustion turbine engines, particulary those of the prop-jet type. Mineral oil lubricants containing addedviscosity index improvers, thickeners or other highly nonvolatile additives are undesirable for use in such engines because of the tendency to leave a residue which would accumulate and interfere with the operation of the engine. A synthetic lubricant of the type described in the present specification is especially adapted to use under such conditions, since the lubricant contains no additives and thus tends to leave no residue upon volatilization.

The new compounds of the present invention,

which are distinguished for exhibiting a high viscosity index and very low pour points, are esters of aliphatic dibasic acids, characterized by the presence of at least one oxygen atom and a branched chain hydrocarbon structure in each ester group.

Esters of the above; typemaybe formed by esterifying the dibasic acids with ether-alcohols obtained by reacting aliphatic monohydric alco- If, then, this product is reacted with a typical dibasic acid such as adipic acid, the resulting product will consist of mixtures of the following three compounds:

and

on, on, I 000 114111200113 o'ooom-tuoon, (0H1); Hi).

CH3 CH3 OO(IJH-CH2OCH3 oocnr-cnocni CHI coodH-omocm on, oocuz-cinoom If more than one mol of alkylene oxide is reacted with the monohydric alcohol, ether alcohols will be formed having more than one ether linkage in the molecule, and such compounds may be likewise employed in the formation of the 'esters' of the present invention. One series ot ether-alcohols formed in this manner are known to the trade as Dowanols.

Since the alkylene oxide to be employed must contain at least three carbon atoms, a branched chain structure results in the ester group. Obviously, when a mixture of the ether-alcohols is reacted with a dibasic acid, a mixture of esters will be formed, but such mixtures will be suitable for use as synthetic lubricants in the same manner as pure esters.

The new class of esters forming the subject matter of the present invention may be defined by the formula a oo (c O)R R5 R1 fishnet I ls is n As can be seen from the formula,

bon atoms, at least one being an alkyl group;

R and R each represent an aliphatic hydrocarbon radical, saturated-or unsaturated, straight chain or branched; n and n areintegers; and

the sum of the carbon and oxygen atoms in each group (Elite 16 8 n and is to 26.

' with Water. After drying over a desiccant, such as anhydrous 02,304, th material is stripped at r "a pressure of 5 mm. to a bath temperature of the esters of Q The data obtained in the tests of properties 6f the esters obtained as described are shown in the table.

Table Mols Oxide per Mol Alcohol Alcohol 'Oxide Isopropyl Do 1 HzooowwmH the present invention may be prepared from any of the paraffin dicarboxylic acids containing from 2 to 28 carbon atoms. Where R of the formula contains no carbon atoms, the acid employed is oxalic acid. Among the acids which may be employed are, for example, oxalic, malonic, succinic, pyrotartaric, dimethylsuccinic, trimethylsuccinic, glutaric, adipic, trimethyladipic, suberic, sebacic, and hexadecane dicarboxylic acids, as well as unsaturated acids such as maleic acid, fumeric acid, and alkenyl succinic acids, the last named being formed by condensing olefins with maleic anhydride. 7

,The alcohols which may be employed in the esterification of the dicarboxylic acids are of the type which are formed by reacting anyof the monobasie aliphatic alcohols, whether primary, secondary, or tertiary, with propylene oxide, 1,2- or 2,3-butylene oxide, or isobutylene oxide, the chain length of the alcohol and the number of molecular proportions of alkylene oxide for each molecular proportion of alcohol being limited by Acid Propylene- Sebacie.

the provision, in accordance with the general formula shown above, that the total vof-carbon and oxygen atoms in each ester group should not exceed 20. Among the alcohols Which are of most particular interest in the preparation of the new esters may be mentioned methyl, ethyl, n-'propyl, isopropyl, n-butyl, isobutyl, sec.-buty1, tert.-butyl, n-amyl, iso-amyl, sec.-amyl, tertamyl, 2-ethylbutyl, n-octyl, tert.-octyl, Z-ethylhexyl, n-decyl, cetyl, lauryl, and oleyl alcohols.

The esterification process can be carried out by the usual methods, preferably employing an esterification catalyst such as p-toluenesulfonic acid and a water-entraining agent.

In the table below will be shown data obtained in tests of the properties of seven typical esters illustratingthe present invention, these esters having been formed by first preparing an ether- 7 alcohol by reacting methyl or isopropyl alcohol with one, two and three molecular proportions, respectively, of propylene oxide, and then preparing di-esters of sebacic or adipic acid by esterifying the acid with the alcohols prepared Flash Kinematic Viscosity Point 0 The above data show that the esters which were tested possess unusually valuable properties with respect to their usefulness as synthetic lubricating oils. j

The esters of the present invention may be employed not only as such but also in mixtures with mineral oils to produce lubricants of su'perior properties with respect to viscosity index, pour point, and other desirable characteristics. What is claimed is: 1. A composition of matter having the formula COO(E E O)R IL 1 l1 LOOGLQW where R is an alkylene group containing 4 to S carbon'atoms; where one of the groups R1 and R2 in each esterifying radical is a methyl group and the other is hydrogen; where R is an alkyl groupcontaining 1 to 3 carbon atoms; and where n is an integer from 1 to 3.

' 2. A composition according to claim 1 in which R is the group --(CHz)a-', and where R is an isopropyl radical.

3. A composition according to claim 2 in which n of the formula is 1.

4. A composition according to claim 2 in which n of the formula is 2.

5. A composition according to claim 1 in which R is the group -(CH2)4-, in which R is a methyl radical, and in which n is 3. I

' PAUL V. SMITH, JR.

FRED KNOTH, JR.

REFERENCES CITED UNITED STATES PATENTS Number D t 1 Name 1,706,639 Van Schaack Mar. 26, 1929 2,118,506 Graves May 24, 1938 

1. A COMPOSITION OF MATTER HAVING THE FORMULA 